HIV-1 infection and mucosal immunity are intimately interrelated. Since the acquisition of HIV-1 primarily occurs through mucosal routes, local immunity at the site of infection is essential for controlling viral spread within the host and in transmitting virus to other individuals. Additionally, established HIV-1 infection compromises both innate and adaptive mucosal immunity, facilitating secondary infections and progression to acquired immune deficiency syndrome (AIDS). Thus, if we are to develop an effective vaccine for HIV-1 that protects the key target cells in the mucosa, we first need to understand how to induce protective anti-HIV-1 mucosal immune responses. We recently discovered a novel subset of tonsil and gut innate immune cells that express natural killer (NK) cell markers, but, in contrast to conventional NK cells, produce interleukin (IL)-22 and other cytokines that protect the integrity of the mucosal barriers during infectious and inflammatory diseases. We refer to these cells as NK-22 (Cella M, et al, Nature. 2009;457:722). Our preliminary data indicate that NK-22 cells directly counter HIV-1 replication in infected CD4 T cells in vitro. We also demonstrate that NK-22 cells secrete BAFF, a soluble factor that enhances B cell responses. Based on their unique properties, we propose that NK-22 cells may be crucial for innate and adaptive anti-HIV-1 mucosal responses. In our proposal we will determine the mechanisms by which NK-22 cells counter HIV-1 infection (specific aim 1), identify vaccine adjuvants that expand NK-22 cells in the mucosa (specific aim 2), and determine the impact of NK-22 cells on adaptive B cell responses against HIV-1 (specific aim 3). We are uniquely positioned to successfully address these aims because of our original discovery of human NK-22 cells, our broad expertise in NK cell biology, the strength of our preliminary data, the relatively straightforward experiments that we have chosen and the availability of reagents through our collaboration with the Center for HIV/AIDS Vaccine Immunology (CHAVI). Our proposal will significantly advance our knowledge of anti-HIV-1 mucosal immune responses and identify adjuvants that can be used to generate vaccines for HIV-1 that elicit effective mucosal immunity. PUBLIC HEALTH RELEVANCE: We recognize that HIV-1 infection affects human mucosae, including the urogenitary and gastro-intestinal tract. Therefore, if we are to develop an effective vaccine for HIV-1 that protects the mucosae, we first need to understand how to induce protective anti-HIV-1 mucosal immunity. We have recently discovered a novel subset of cells of the immune system, which we call NK-22, that enhance mucosal immunity, particularly against HIV- 1. In our proposal we will determine the mechanisms by which NK-22 cells counter HIV- 1 infection and identify molecules that can be used as adjuvants of anti-HIV-1 vaccines to expand NK-22 cells. These studies will help to design better anti-HIV-1 vaccines.